Fluid-propelled direct-acting engine.



W. MAUSS. FLUID PROPELLED DIRECT ACTING ENGINE.

APPLIUATION FILED AUG.24, 1908.

Patented Aug. 23, 1910.

WILHELM MAUSS,

OF BRAKPAN,

TRANSVAAL.

FLUID-PROPELLED DIRECT-ACTING ENGINE.

To all whom it may concern:

Be it known that I, VILHELM MAUss, engineer, a subject of the King of Great Britain, residing at Brakpan, Transvaal, have invented certain new and useful Improvements in Fluid-Propelled Direct-Acting Engines, of which the following is a specication.

The present invention has reference to fluid actuated percussive machines having means enabling short strokes to be made, under appropriate conditions, by curtailing the rearward movement of the piston; said means including as an essential feature a small hole permitting leakage of the actuating fluid. Such shortening of the rearward stroke is provided for in order that light strokes may be delivered when starting work and also to enable a rock drill to clear itself when it is so clogged as to be incapable of a complete backward stroke.

A valve device of the usual common type in which pressure is admitted to and exhausted from each side of the valve alternately, and adapted to work in the manner stated was described in Patent No. 844,161.

The purpose of the present invention is to adapt a differential valve to operate as described, and thereby produce a valve arrangement which is simpler than that described in the prior pat-ent.

In the accompanying drawings the invention is shown as applied to a rock drilling machine having the valve internal of the piston; Figure I being a longitudinal section of one form, and Figs. II and III similar views of modifications.

The piston 1 is provided with a relatively large front pressure area 2 and a smaller annular rear pressure area 3 formed by cutting oft` the central portion of the rear piston face by means of a trunk 4 which preferably forms a part of the -piston as shown, but

the piston.

5 indicates the piston rod and 6 the cylinderv corresponding in shape to the piston working therein. Y

, Actuating fluid is constantly supplied to the area 3;' and as the machine illustrated is 1 intended to be fed forward in an encirclingv shell by pressure of actuating fluid at its rear, the supply for said area 3 is conducted through plain holes 7 formed in the shoulder of the cylinder; or when cushioning on the back stroke is required, through Specification of Letters Patent.

Application filed August 24, 1908.

Patented Aug. 23, 1910.

seriai No. 450,084.

holes 8 placed as shown, tov which access is had by a groove 9.0n the periphery of the cylinder. The supply and exhaust of the fluid to and from the frontcylinder space is controlled by the valve 10. Said valve is located within the piston and is of the dify ferential type, 2'. e. one of its actuating pressure surfaces is acted upon by a constant total fluid pressure which is less than the total `pressure which may be applied to its other actuating pressure surface. This result may be effected either by employing the same unit pressure on each such pressure surface and differentiating the areas thereof (as 1n the examples hereafter described), or by causing, in known ways, different unitpressures to actupon equal pressure surfaces. wWhere the expression differential valve is employed in this speciication without restriction, it is intended to mean either construction described.

In the example illustrated in Fig. I the i' pressure surface 11 is of less area than the opposite face 12, and is constantly supplied with pressure by means of channelll. The area 12 is put into communication'with the annular recess 14 on the peripheryofA the piston by channel 15, and a small channel 16 connects the peripheral recess with the front pressure space of t-he cylinder. The valve is hollow and its interior communicates with i front face of the piston. may be a stationary part telescoping within v A hole 23 is in some cases drilled in from the peripheryof the piston rod to the axial bore 17 therein; and a series of slots 24 afford communication between the constant `pressure space and the recess 14 when the piston is at the front of its stroke.

In ordinary operation, the piston being at the rear end of its stroke, actuating'uid,

y hereafter named air, is supplied through y ports 7 and passing through channel 13y acts on the small valve surface 11. There being no pressure in the front cylinder and consequently none on the larger valve surface 12,

the valve is held to the rear of its travel,l

thereby shutting off port 21 from port 22, which latter is in connection with the exhaust holes 20. Pressure of air acting upon the piston face 3 drives the piston forward to deliver its blow. Immediately prior to or simultaneously with the blow being struck, when the piston reaches the position shown in Fig. I, air passes from the constant pressure space by way of the slots 24, recess 14 and channel 15 to the large area 12 of the valve, which is thereby thrown forward. This operation permits air to pass through the ports 21 and 22 to the front of the piston, and acting on the relatively larger area 2, to drive the piston back. In moving backward the piston shuts ofl' the slots 24, but the valve is still held in position by pressure from the front cylinder space being transmitted through the small channel 16, which while being of the requisite area for the purpose is kept sufliciently small to prevent any material amount of live air from passing from the recess 14 into the front cylinder and thence to exhaust through 22 and 18, before the valve has had time to throw over. As the piston continues its backward movement, port 21 is covered by the smaller cylinder member and the supply to the front cylinder space being thereby cut off, the stroke is completed by expansion of the air therein, assisted of course by the momentum of the piston.

vWhen the holes 23 are provided, they come into the front cylinder space at or near the termination of the rearward stroke and by affording a temporary free exhaust independently of the valve, enhance the freedom of the forward stroke. Moreover by insuring the necessary reduction of pressure in the front cylinder at t-he end of the stroke hereafter referred to, they assist the ready actuation of the valve. They are not however essential.

The diminution of pressure at the end of the rearward stroke, due to expansion, causes the constant pressure on the face 11 of the valve to preponderate over that existing on the other face of the valve, which is thus once more reversed; thus eecting or maintaining the exhaust from the front cylinder through 22 and 18 and remaining so throughout the forward stroke, which is effected by the constant pressure on face 3, as already explained.

Both valve pressure surfaces are, in the above case, formed at the front end of the valve in order to avoid interference between the actuating channels 13 and 15, and the port 21, the longitudinal part of which is formed by an annular depression turned on the piston bush 25. A modified form of valve which presents certain advantages owing to some pressure being applied to the rear thereof is shown in Fig. II. In this case the area of the face 12 is diminished and the rear end of the valve is modified so that the face 26 is constituted an additional variable pressure surface. Said face 26 is constantly in communication with port 21, so that when the latter opens into the constant pressure space during the forward stroke of the piston, live air passes to face 26 and by nearly balancing the pressure on face 11 enables a rapid reversal of the valve to occur when the face 12 receives pressure at the end of the stroke. Vith the valve in the forward position, both faces 12 and 26 are in communication with the front cylini der and the reversal of the valve at the end of the rearward piston stroke is therefore effected in the manner already described.

28 indicates a small hole drilled into the bore of the piston rod from the periphery thereof, at such a point as to enter the front cylinder space immediately or otherwise after cut off has beeneffected by closure of port 21 by the cylinder shoulder. The size of hole 28 is such that no important amount i by the sticking of the drill or when the air supply is intentionally throttled, such escape will reduce the pressure in the front cylinder suiiiciently to enable the valve to be reversed and thus cause the piston to be driven forward.

A more elastic arrangement for effecting the same result is shown in Fig. III. The general arrangement is identical with that shown in Fig. I, the dierences being, firstly, that channel 16 is omitted altogether, or in other ways communication between the valve face 12 and the front cylinder is cut off during the rearward stroke; and secondly a very small hole 27 is bored adjacent to said face, through to the center of the valve. It will now be seen that in the event of the piston hanging or stopping on its rearward stroke at any time after slots 24 are closed by the piston, pressure on face 12 will in a short time be dissipated through hole 27, and the constant pressure on 11 will then throw the valve to exhaust the front cylinder, and a fresh forward stroke will occur. As a rule the hole 27 would be so proportioned that in normal working its iniuence o from pressure supplied through ports 22. This arrangement is improved by cutting a slot 42 in the piston rod forwardly from its junction with the piston. The length of this slot is such that when the shoulder has entered so far into recess l1 that the cushion of air trapped therein has reduced the speed of the piston to a safe limit, such cushioned air is conducted by the slot to an annular groove 48 in the neck of the cylinder head and thence exhausted through the holes 23 or otherwise. By this means the greater part of the front piston face is relieved of pressure, without movement of the valve, and the machine is consequently stopped automatically until fed up to the work sufficiently to once more expose the piston face to pressure.

lVhat I claim, and desire to secure by Letters Patent is l. A percussive engine structure comprising in combination, a front cylinder portion for the structure adapted for expansive working of pressure fluid, a differential distributing valve having a relatively reduced pressure surface acted upon by constant fluid pressure tending to exhaust the front cylinder portion, said valve having a pressure surface relatively enlarged with respect to said reduced pressure surface, means for admitting pressure fluid intermittently to said -enlarged pressure surface to move the valve for feeding the front cylinder portion, and leakage means tending to exhaust pressure from the relatively enlarged surface of the valve to permit the valve to be moved by the constant pressure to a position for exhausting the front cylinder portion.

2. In a percussive engine, the combination of a dierential ldistributing valve having constant pressure on its lesser pressure surface tending to exhaust the front cylinder, means for supplying pressure fiuid to the greater pressure surface of the valve to move the same to feed the front cylinder, said supply tothe valve being cut off during the rearward stroke of the piston, and a constant small leakage from the greater pressure surface of the valve.

3. In a percussive engine, a differential distributing valve having constant pressure on its lesser pressure surface tending to exhaust the front cylinder, means for admitting pressure fluid to the greater pressure surface of the valve to feed the front cylinder, said admission to the valve being cut off during the rearward stroke of the piston, and 'a constant small leakage from the greater pressure surface of the valve, the rate of such leakage being such as to cause the valve to be reversed at the termination of the rearward piston stroke when the piston is moving normally.-

4. In a percussive engine, a differential valve controlling exhaust from the front cylinder, said valve having constant pressure on its lesser pressure surface, by which it is moved to exhaust the front cylinder, means for admitting pressure intermittently to the greater pressure surface of the valve to close said exhaust, and a constant small leakage from the last named valve surface.

5. In a percussive engine, having a cylinder, a distributing valve, the position of which is determined by the degree of pressure in the front end of the cylinder; means independent of the valve whereby pressure in the front end of the cylinder is exhausted before the completion of a normal rearward stroke; for the purpose specified.

6. In a percussive engine, a piston having constant pressure on its rear face, and having a shoulder turned on its front face, means for supplying fluid at such shoulder about the termination of a normal forward stroke to effect the rearward stroke, a recess in the cylinder head into which the shoulder passes upon the piston making an abnormally long forward stroke and means operating when the shoulder has passed partially into the recess to exhaust pressure therefrom.

In testimony whereof I aflix my signature in presence of two witnesses.

WILHELM MAUSS.

Witnesses:

IVESLEY E. JOHN, J. WARREN VENNING. 

